rust-lang · tgross35 · Aug 9, 2025 · Aug 9, 2025 · Aug 10, 2025 · Aug 10, 2025
diff --git a/.editorconfig b/.editorconfig
@@ -8,20 +8,23 @@ root = true
 end_of_line = lf
 charset = utf-8
 insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+indent_size = 4
 
 # some tests need trailing whitespace in output snapshots
-[!tests/]
-trim_trailing_whitespace = true
+[tests/**]
+trim_trailing_whitespace = false
 # for actual source code files of test, we still don't want trailing whitespace
 [tests/**.{rs,js}]
 trim_trailing_whitespace = true
 # these specific source files need to have trailing whitespace.
 [tests/ui/{frontmatter/frontmatter-whitespace-3.rs,parser/shebang/shebang-space.rs}]
 trim_trailing_whitespace = false
 
-[!src/llvm-project]
-indent_style = space
-indent_size = 4
+[src/llvm-project]
+indent_style = unset
+indent_size = unset
 
 [*.rs]
 max_line_length = 100

diff --git a/compiler/rustc_lexer/src/lib.rs b/compiler/rustc_lexer/src/lib.rs
@@ -331,24 +331,37 @@ pub fn is_whitespace(c: char) -> bool {
 
     matches!(
         c,
-        // Usual ASCII suspects
-        '\u{0009}'   // \t
-        | '\u{000A}' // \n
+        // End-of-line characters
+        | '\u{000A}' // line feed (\n)
         | '\u{000B}' // vertical tab
         | '\u{000C}' // form feed
-        | '\u{000D}' // \r
-        | '\u{0020}' // space
-
-        // NEXT LINE from latin1
-        | '\u{0085}'
+        | '\u{000D}' // carriage return (\r)
+        | '\u{0085}' // next line (from latin1)
+        | '\u{2028}' // LINE SEPARATOR
+        | '\u{2029}' // PARAGRAPH SEPARATOR
 
-        // Bidi markers
+        // `Default_Ignorable_Code_Point` characters
         | '\u{200E}' // LEFT-TO-RIGHT MARK
         | '\u{200F}' // RIGHT-TO-LEFT MARK
 
-        // Dedicated whitespace characters from Unicode
-        | '\u{2028}' // LINE SEPARATOR
-        | '\u{2029}' // PARAGRAPH SEPARATOR
+        // Horizontal space characters
+        | '\u{0009}'   // tab (\t)
+        | '\u{0020}' // space
+    )
+}
+
+/// True if `c` is considered horizontal whitespace according to Rust language definition.
+pub fn is_horizontal_whitespace(c: char) -> bool {
+    // This is Pattern_White_Space.
+    //
+    // Note that this set is stable (ie, it doesn't change with different
+    // Unicode versions), so it's ok to just hard-code the values.
+
+    matches!(
+        c,
+        // Horizontal space characters
+        '\u{0009}'   // tab (\t)
+        | '\u{0020}' // space
     )
 }
 
@@ -538,7 +551,7 @@ impl Cursor<'_> {
         debug_assert!(length_opening >= 3);
 
         // whitespace between the opening and the infostring.
-        self.eat_while(|ch| ch != '\n' && is_whitespace(ch));
+        self.eat_while(|ch| ch != '\n' && is_horizontal_whitespace(ch));
 
         // copied from `eat_identifier`, but allows `-` and `.` in infostring to allow something like
         // `---Cargo.toml` as a valid opener
@@ -547,7 +560,7 @@ impl Cursor<'_> {
             self.eat_while(|c| is_id_continue(c) || c == '-' || c == '.');
         }
 
-        self.eat_while(|ch| ch != '\n' && is_whitespace(ch));
+        self.eat_while(|ch| ch != '\n' && is_horizontal_whitespace(ch));
         let invalid_infostring = self.first() != '\n';
 
         let mut found = false;
@@ -588,7 +601,7 @@ impl Cursor<'_> {
                 // on a standalone line. Might be wrong.
                 while let Some(closing) = rest.find("---") {
                     let preceding_chars_start = rest[..closing].rfind("\n").map_or(0, |i| i + 1);
-                    if rest[preceding_chars_start..closing].chars().all(is_whitespace) {
+                    if rest[preceding_chars_start..closing].chars().all(is_horizontal_whitespace) {
                         // candidate found
                         potential_closing = Some(closing);
                         break;

diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
@@ -6,7 +6,7 @@ use rustc_ast::util::unicode::{TEXT_FLOW_CONTROL_CHARS, contains_text_flow_contr
 use rustc_errors::codes::*;
 use rustc_errors::{Applicability, Diag, DiagCtxtHandle, StashKey};
 use rustc_lexer::{
-    Base, Cursor, DocStyle, FrontmatterAllowed, LiteralKind, RawStrError, is_whitespace,
+    Base, Cursor, DocStyle, FrontmatterAllowed, LiteralKind, RawStrError, is_horizontal_whitespace,
 };
 use rustc_literal_escaper::{EscapeError, Mode, check_for_errors};
 use rustc_session::lint::BuiltinLintDiag;
@@ -597,7 +597,7 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
 
         let last_line_start = within.rfind('\n').map_or(0, |i| i + 1);
         let last_line = &within[last_line_start..];
-        let last_line_trimmed = last_line.trim_start_matches(is_whitespace);
+        let last_line_trimmed = last_line.trim_start_matches(is_horizontal_whitespace);
         let last_line_start_pos = frontmatter_opening_end_pos + BytePos(last_line_start as u32);
 
         let frontmatter_span = self.mk_sp(frontmatter_opening_pos, self.pos);
@@ -640,7 +640,7 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
             });
         }
 
-        if !rest.trim_matches(is_whitespace).is_empty() {
+        if !rest.trim_matches(is_horizontal_whitespace).is_empty() {
             let span = self.mk_sp(last_line_start_pos, self.pos);
             self.dcx().emit_err(errors::FrontmatterExtraCharactersAfterClose { span });
         }

diff --git a/compiler/rustc_resolve/src/ident.rs b/compiler/rustc_resolve/src/ident.rs
@@ -422,6 +422,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         // to detect potential ambiguities.
         let mut innermost_result: Option<(NameBinding<'_>, Flags)> = None;
         let mut determinacy = Determinacy::Determined;
+        let mut extern_prelude_item_binding = None;
+        let mut extern_prelude_flag_binding = None;
         // Shadowed bindings don't need to be marked as used or non-speculatively loaded.
         macro finalize_scope() {
             if innermost_result.is_none() { finalize } else { None }
@@ -558,15 +560,21 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     Scope::ExternPreludeItems => {
                         // FIXME: use `finalize_scope` here.
                         match this.reborrow().extern_prelude_get_item(ident, finalize.is_some()) {
-                            Some(binding) => Ok((binding, Flags::empty())),
+                            Some(binding) => {
+                                extern_prelude_item_binding = Some(binding);
+                                Ok((binding, Flags::empty()))
+                            }
                             None => Err(Determinacy::determined(
                                 this.graph_root.unexpanded_invocations.borrow().is_empty(),
                             )),
                         }
                     }
                     Scope::ExternPreludeFlags => {
                         match this.extern_prelude_get_flag(ident, finalize_scope!().is_some()) {
-                            Some(binding) => Ok((binding, Flags::empty())),
+                            Some(binding) => {
+                                extern_prelude_flag_binding = Some(binding);
+                                Ok((binding, Flags::empty()))
+                            }
                             None => Err(Determinacy::Determined),
                         }
                     }
@@ -686,7 +694,16 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                                 } else {
                                     None
                                 };
-                                if let Some(kind) = ambiguity_error_kind {
+                                // Skip ambiguity errors for extern flag bindings "overridden"
+                                // by extern item bindings.
+                                // FIXME: Remove with lang team approval.
+                                let issue_145575_hack = Some(binding)
+                                    == extern_prelude_flag_binding
+                                    && extern_prelude_item_binding.is_some()
+                                    && extern_prelude_item_binding != Some(innermost_binding);
+                                if let Some(kind) = ambiguity_error_kind
+                                    && !issue_145575_hack
+                                {
                                     let misc = |f: Flags| {
                                         if f.contains(Flags::MISC_SUGGEST_CRATE) {
                                             AmbiguityErrorMisc::SuggestCrate

diff --git a/compiler/rustc_target/src/spec/targets/loongarch64_unknown_none.rs b/compiler/rustc_target/src/spec/targets/loongarch64_unknown_none.rs
@@ -17,7 +17,7 @@ pub(crate) fn target() -> Target {
         arch: "loongarch64".into(),
         options: TargetOptions {
             cpu: "generic".into(),
-            features: "+f,+d".into(),
+            features: "+f,+d,-lsx".into(),
             linker_flavor: LinkerFlavor::Gnu(Cc::No, Lld::Yes),
             linker: Some("rust-lld".into()),
             llvm_abiname: "lp64d".into(),

diff --git a/library/Cargo.lock b/library/Cargo.lock
@@ -327,7 +327,8 @@ dependencies = [
  "rustc-demangle",
  "std_detect",
  "unwind",
- "wasi",
+ "wasi 0.11.1+wasi-snapshot-preview1",
+ "wasi 0.14.3+wasi-0.2.4",
  "windows-targets 0.0.0",
 ]
 
@@ -399,6 +400,17 @@ dependencies = [
  "rustc-std-workspace-core",
 ]
 
+[[package]]
+name = "wasi"
+version = "0.14.3+wasi-0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a51ae83037bdd272a9e28ce236db8c07016dd0d50c27038b3f407533c030c95"
+dependencies = [
+ "rustc-std-workspace-alloc",
+ "rustc-std-workspace-core",
+ "wit-bindgen",
+]
+
 [[package]]
 name = "windows-sys"
 version = "0.59.0"
@@ -475,3 +487,13 @@ name = "windows_x86_64_msvc"
 version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "589f6da84c646204747d1270a2a5661ea66ed1cced2631d546fdfb155959f9ec"
+
+[[package]]
+name = "wit-bindgen"
+version = "0.45.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "052283831dbae3d879dc7f51f3d92703a316ca49f91540417d38591826127814"
+dependencies = [
+ "rustc-std-workspace-alloc",
+ "rustc-std-workspace-core",
+]
diff --git a/library/alloc/src/borrow.rs b/library/alloc/src/borrow.rs
@@ -17,9 +17,11 @@ use crate::fmt;
 use crate::string::String;
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, B: ?Sized> Borrow<B> for Cow<'a, B>
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<'a, B: ?Sized> const Borrow<B> for Cow<'a, B>
 where
     B: ToOwned,
+    B::Owned: [const] Borrow<B>,
 {
     fn borrow(&self) -> &B {
         &**self
@@ -326,9 +328,10 @@ impl<B: ?Sized + ToOwned> Cow<'_, B> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<B: ?Sized + ToOwned> Deref for Cow<'_, B>
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<B: ?Sized + ToOwned> const Deref for Cow<'_, B>
 where
-    B::Owned: Borrow<B>,
+    B::Owned: [const] Borrow<B>,
 {
     type Target = B;
 
@@ -439,7 +442,11 @@ where
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized + ToOwned> AsRef<T> for Cow<'_, T> {
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
+impl<T: ?Sized + ToOwned> const AsRef<T> for Cow<'_, T>
+where
+    T::Owned: [const] Borrow<T>,
+{
     fn as_ref(&self) -> &T {
         self
     }

diff --git a/library/alloc/src/collections/mod.rs b/library/alloc/src/collections/mod.rs
@@ -128,17 +128,19 @@ pub use realalloc::collections::TryReserveErrorKind;
     reason = "Uncertain how much info should be exposed",
     issue = "48043"
 )]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 #[cfg(not(test))]
-impl From<TryReserveErrorKind> for TryReserveError {
+impl const From<TryReserveErrorKind> for TryReserveError {
     #[inline]
     fn from(kind: TryReserveErrorKind) -> Self {
         Self { kind }
     }
 }
 
 #[unstable(feature = "try_reserve_kind", reason = "new API", issue = "48043")]
+#[rustc_const_unstable(feature = "const_convert", issue = "143773")]
 #[cfg(not(test))]
-impl From<LayoutError> for TryReserveErrorKind {
+impl const From<LayoutError> for TryReserveErrorKind {
     /// Always evaluates to [`TryReserveErrorKind::CapacityOverflow`].
     #[inline]
     fn from(_: LayoutError) -> Self {

diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
@@ -107,10 +107,10 @@
 #![feature(char_max_len)]
 #![feature(clone_to_uninit)]
 #![feature(coerce_unsized)]
+#![feature(const_convert)]
 #![feature(const_default)]
 #![feature(const_eval_select)]
 #![feature(const_heap)]
-#![feature(const_trait_impl)]
 #![feature(core_intrinsics)]
 #![feature(deprecated_suggestion)]
 #![feature(deref_pure_trait)]
@@ -168,6 +168,7 @@
 #![feature(allow_internal_unstable)]
 #![feature(cfg_sanitize)]
 #![feature(const_precise_live_drops)]
+#![feature(const_trait_impl)]
 #![feature(coroutine_trait)]
 #![feature(decl_macro)]
 #![feature(dropck_eyepatch)]

diff --git a/library/alloctests/lib.rs b/library/alloctests/lib.rs
@@ -49,6 +49,7 @@
 // Language features:
 // tidy-alphabetical-start
 #![feature(cfg_sanitize)]
+#![feature(const_trait_impl)]
 #![feature(dropck_eyepatch)]
 #![feature(lang_items)]
 #![feature(min_specialization)]